Hydraulic cylinder with boosting function

ABSTRACT

A fluid pressure cylinder with pressure intensifying function, has an oil-filled hydraulic pressure cylinder which is filled with oil and tightly sealed. A gas-filled gas spring is charged with gas and tightly sealed. By means of gas spring, oil in oil chamber of hydraulic pressure cylinder is pressurized to a pressure level higher than the gas pressure in gas actuating chamber of gas spring. This results in a strong pushing force being generated via output piston of hydraulic pressure cylinder.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a fluid pressure cylinder with apressure-intensifying function. more particularly, the present inventionrelates to a fluid pressure cylinder wherein the fluid pressure insidethe fluid pressure cylinder is pressurized to high pressure by means ofa gas spring.

BACKGROUND OF THE INVENTION

Conventionally, gas springs are used in a variety of mechanisms, such asshock-absorbing/damping mechanisms for press machines, mechanisms forelastic die supports used in multi-stage drawing fabrications, and thelike. Gas springs, in general, have a cylinder, a gas actuating chamberwithin this cylinder filled with compressed nitrogen gas, and apressure-receiving part which receives the gas pressure of this gasactuating chamber. An output rod, integral with the pressure-receivingpart, extends to the exterior of the cylinder and is pushed to theprotruding side by the gas pressure of above-indicated compressednitrogen gas.

For example, where a gas spring is applied as a damping mechanism in apress machine, a damping action is obtained by having the moving parts,such as the press slides, pull out/push in the output rod in oppositionto the pushing of the gas pressure of the gas spring. Filling the gasactuating chamber of the gas spring with compressed nitrogen gas isusually done using an existing gas tank. The gas pressure inside a gastank is 10 MPa˜15 MPa, and, due to the relationship that as gas isconsumed the gas pressure drops, the gas pressure of the compressed gaswhich fills the gas actuating chamber is set at a gas pressure (forexample, 7 Mpa) lower than the gas pressure within the gas tank.

With a conventional gas spring, it is difficult to fill the gasactuating chamber with high-pressure compressed nitrogen gas. As aresult, to be able to generate a strong pushing force and support alarge load, it is necessary to have a large gas spring. Such springswill not fit in small spaces and their production costs are high. On theother hand, if the gas pressure of the compressed nitrogen gas whichfills the gas actuating chamber is made excessively high, problemsoccur, such as leakage of the compressed nitrogen gas to leak to theoutside.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide apressure-intensifying fluid pressure cylinder which overcomes theforegoing problems.

It is another object of the present invention to pressurize, by means ofa gas spring, the liquid in a liquid pressure cylinder to a pressurehigher than the gas pressure in the gas actuating chamber. This enablesgeneration of a strong pushing force, thus enabling the support of largeloads.

It is a further object of the present invention to provide a fluidpressure cylinder having reduced size, reduced production cost.

It is yet another object of the present invention to provide a fluidpressure cylinder to enable a reset action by means of liquid pressure.

The fluid pressure cylinder with a pressure-intensifying function of thepresent invention comprises a cylinder body; a liquid chamber formedwithin the cylinder body, filled with liquid; an output piston whichreceives the liquid pressure of this liquid chamber; a gas spring havinga gas actuating chamber filled with compressed gas and apressure-receiving means which receives the gas pressure of the gasactuating chamber; wherein the gas spring can pressurize the liquid insaid liquid chamber to a pressure higher than said gas pressure.

It is desirable to use oil as the above-mentioned liquid and compressednitrogen gas as the above-mentioned compressed gas. The gas actuatingchamber of the gas spring is filled with compressed gas and thepressure-receiving device receives this gas pressure. The liquid chamberis formed within the cylinder body of the liquid pressure cylinder. Bymeans of the gas spring, the liquid contained in the liquid chamber, ispressurized, via a pressure-receiving device, to a pressure higher thanthe gas pressure of the gas actuating chamber. The pressurized liquidpressure is received by an output piston.

As the gas spring pressurizes the liquid in the liquid pressure cylinderto a pressure higher than the gas pressure in the gas actuating chamber,it becomes possible to generate a strong pushing force and support heavyloads. By charging the gas actuating chamber with compressed gas from anexisting compressed gas supply source, such as a gas tank, the liquidpressure of the liquid chamber can be intensified by several times bymeans of the pushing force of the gas spring, making it possible togenerate the above-mentioned strong pushing force. As a result, thestructure of a fluid pressure cylinder with a spring function can bemade smaller, resulting in advantages in preventing leaks of thecompressed gas and lower production costs.

According to a feature of the present invention, it is desirable thatthe above-mentioned gas spring cylinder part be formed integrally withthe above-mentioned cylinder body and the gas spring and liquid pressurecylinder be position in a straight line pattern. In this case, the fluidpressure cylinder with pressure-intensifying function can be made as asimple structure enabling a reduced production cost.

According to a feature of the present invention, inside theabove-mentioned cylinder body, a partitioning means may be providedwhich separates the liquid chamber and gas actuating chamber. Thispartitioning means may be secured to the cylinder body by a threadedfit. In this case, in a cylinder body formed integrally with thecylinder part, it is easy to form a liquid chamber and a gas actuatingchamber.

In addition, a passage hole maybe formed in above-mentioned partitioningmeans into which the output rod of the pressure-receiving means isslidably inserted. In this case, the end of the output rod can be madeto contact the liquid in the liquid chamber and surely pressurize thatliquid.

In addition, to retract the pressure-receiving means, a “liquid chamberfor retraction” may be provided in above-mentioned gas spring,configured such that by supplying liquid pressure to the liquid chamberfor retraction, the pressure-receiving means is made to retract. In thiscase, even without applying a strong external force to the output pistonin opposition to above-mentioned strong urging force, by supplyingliquid pressure of a comparatively low pressure to the liquid chamberfor retraction, the pressure-receiving means can be easily retracted.

In addition, in the above-mentioned liquid pressure cylinder, a springdevice may be provided to put force on the output piston in theretracting direction. In this case, by making the pressure-receivingmeans retract, the output piston can surely be made to retract due tothe force of the spring device.

In addition, it is desirable that above-mentioned liquid chamber forretraction be formed between above-mentioned partitioning means and thepressure-receiving part of the pressure-receiving means. In this case,because the pressure-receiving part of the pressure-receiving means canbe made to receive the liquid pressure of the liquid chamber forretraction, the pressure-receiving means can be retracted by supplyinghydraulic pressure at a comparatively low pressure to the liquid chamberfor retraction.

The above, and other objects, features and advantages of the presentinvention will become apparent from the following description read inconjunction with the accompanying drawings, in which like referencenumerals designate the same elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-section diagram of the fluid pressurecylinder with pressure-intensifying function (in its extended state)relating to an embodiment of the present invention.

FIG. 2 is a vertical cross-section diagram of the fluid pressurecylinder of FIG. 1 (in its retracted state).

FIG. 3 is a vertical cross-section diagram of the fluid pressurecylinder of a first alternative embodiment of the present invention (inits extended state).

FIG. 4 is a vertical cross-section diagram of the fluid pressurecylinder of FIG. 3 (in its retracted state).

FIG. 5 is a vertical cross-section diagram of multiple fluid pressurecylinders and the base plate of a second alternative embodiment of thepresent invention.

FIG. 6 is a vertical cross-section diagram of a clamping apparatus (inits clamped state) equipped with a fluid pressure cylinder according toa third alternative embodiment of the present invention.

FIG. 7 is a vertical cross-section diagram of the clamping apparatus ofFIG. 6 (in its clamp released state).

FIG. 8 is a vertical cross-section diagram of a toolingexchanging/securing apparatus (in its “tool secured” state) equippedwith a fluid pressure cylinder according to a fourth alternativeembodiment of the present invention.

FIG. 9 is a vertical cross-section diagram of the fluid pressurecylinder of FIG. 8 (in its clamped state).

FIG. 10 is a vertical cross-section diagram of the fluid pressurecylinder of FIG. 8 (in its clamp released state).

FIG. 11 is a vertical cross-section diagram of the fluid pressurecylinder according to a fifth alternative embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Below, an embodiment of the present invention will be described,referring to the figures. This embodiment is one example of the case ofapplying the invention to a fluid pressure spring made as ashock-absorbing (damping) mechanism for press machines and the like.

Referring to FIGS. 1 and 2, fluid pressure cylinder withpressure-intensifying function 1 (referred to below as fluid pressurecylinder 1), as a fluid pressure spring, includes an oil containing-typehydraulic pressure cylinder 2, charged with oil L in a tightly sealedstate, and a gas containing-type gas spring 3, charged with compressedgas G in a tightly sealed state. Hydraulic pressure cylinder 2 and gasspring 3 have a common cylinder main body 4 and are arranged in astraight row pattern, one above the other.

Description of Hydraulic Pressure Cylinder 2

Hydraulic pressure cylinder 2 includes a cylinder body 10, which makesup approximately the upper half of cylinder main body 4; an oil chamber11 formed inside cylinder body 10, containing oil L; an output piston 12which receives the hydraulic pressure of oil chamber 11; and apartitioning means 13 which forms the cylinder end wall.

A passage hole 10 b is formed in cover wall 10 a of cylinder body 10 androd 12 a of output piston 12 is inserted in this passage hole 10 b in afreely sliding manner. The space between the surrounding wall whichpassage hole 10 b of cover wall 10 a and rod 12 a is sealed by acircular seal part 9 a and an O-ring 9 b.

Piston 12 has rod part 12 a and a pressure-receiving part 12 b, providedat the bottom end of rod part 12 a. In the lower part of piston 12, fromits lower side, a hole 12 c is formed. The diameter ofpressure-receiving part 12 b is formed larger than the diameter of rodpart 12 a and smaller than the diameter of oil chamber 11, and is heldwithin oil chamber 11. In the state when this pressure-receiving part 12b abuts the lower end of cover wall 10 a (see FIG. 1), piston 12 is atits protruding position which is the maximum limit of upward protrusion.

Partitioning means 13 is fixed in the lower end portion of cylinder body10 by threaded fitting. Specifically, roughly the lower half ofpartitioning means 13 is thread-fitted to the inside wall of cylinderbody 10 and, upward from the threaded fitting portion of partitioningmeans 13 and of the inside wall of cylinder body 10, partitioning means13 is formed with a slightly smaller diameter than these threaded parts.By causing the shoulders where partitioning means 13 changes diameterand inside wall of cylinder body 10 changes diameter to engage with eachother at this border, partitioning means 13, which is thread-fitted intocylinder body 10, is secured in position. The space between the outerperiphery of the upper edge of partitioning means 13 and the inner wallof cylinder body 10 is sealed by O-ring 9 c.

Description of Gas Spring 3

Gas spring 3 comprises a cylinder part 20, a gas actuating chamber 21which has a diameter slightly larger than the diameter ofabove-mentioned oil chamber 11 and is filled with compressed gas G, apressure-receiving means 22 which receives the gas pressure of gasactuating chamber 21, a partitioning means 13 which is common tohydraulic pressure cylinder 2 and at the same time comprises the headcover for gas actuating chamber 21, and cylinder end wall 23. Gas spring3 is configured so that it can pressurize the oil L in oil chamber 11 ofhydraulic pressure cylinder 2 to a higher pressure than above-mentionedgas pressure.

Cylinder part 20 includes cylinder main body 4, which is formedintegrally with cylinder body 10 of hydraulic pressure cylinder 2, andis partitioned into oil chamber 11 and gas actuating chamber 21 bypartitioning means 13.

Pressure-receiving means 22 has a pressure-receiving part 22 ainternally fitted into cylinder part 20 so that it can slide freely, andan output rod 22 b, which extends upward from pressure-receiving part 22a. Circular seal part 9 d is mounted in circular channel formed on thecircumference of pressure accepting part 22 a, and by means of seal part9 d, the space between pressure-receiving part 22 a and the inner wallof cylinder part 20 is sealed. In the lower part of pressure-receivingpart 22 a, concave area 22 d is formed which is concave relative to thelower side of pressure-receiving part 22 a.

Hole output rod part of pressure-receiving means 22 a is slidablyinserted into passage hole 13 a, formed in partitioning means 13. Thespace between the lower part of the wall surface of partitioning means13, which forms passage hole 13 a, and output rod 22 b, is sealed bymeans of an O-ring 9 e. In cylinder part 20, a venting hole 20 a isformed communicating to the gap between partitioning means 13 andpressure-receiving part 22 a.

Cylinder end wall 23 is thread-fitted into the lower end portion ofcylinder part 20, and in its center part, a gas passage hole 23 a,connecting gas actuating chamber 21 to the exterior, is formed. Checkvalve 24 is built into this gas passage hole 23 a, fitted internally ina gas-tight manner. It is configured such that, by means of check valve24, compressed gas in gas actuating chamber 21 is prevented from leakingout and also compressed gas can be supplied to gas actuating chamber 21from an external gas supply source (not shown in the figures), such as agas tank.

Circular concave part 23 b is formed in the top side of the upper partof cylinder end wall 23.

Here, in oil chamber 11 of hydraulic pressure cylinder 2, oil L fillsthe portion surrounded by cylinder body 10, output piston 12,partitioning means 13, and output rod 22 b of pressure-receiving means22, which portion is liquid-tight. While in gas actuating chamber 21 ofgas spring 3, compressed gas G fills the portion surrounded by cylinderpart 20, pressure-receiving part 22 a of pressure-receiving means 22,and cylinder end wall 23, which portion is gas-tight.

When output rod of 22 b of pressure-receiving means 22 moves in and out,piston 12 moves in and out in a “linked” manner, so that the volume ofoil L (oil chamber 11) does not change. Also, in the state (see FIG. 1)where pressure-receiving part 22 a of pressure-receiving means 22 abutsthe lower edge of partitioning means 13, that is, the protrudingposition of pressure-receiving means 22 (upper limit position), andupper part of output rod 22 b protrudes into oil chamber 11, and piston12 also reaches above-mentioned protruding position.

On the other hand, in the state where pressure-receiving part 22 a ofpressure-receiving means 22 abuts the upper edge of cylinder end wall 23(see FIG. 2), pressure-receiving means 22 is at its retracted position(lower limit position), and the end of output rod 22 b goes down intopassage hole 13 a of partitioning means 13 to a position just above thelevel of O-ring 9 e. At that time, output piston 12 also goes to itsretracted position (lower limit position), a state where the end ofoutput piston 12 protrudes slightly to the outside. Furthermore, whenpressure-receiving means 22 is positioned in the retracted position, ingas actuating chamber 21, compressed gas G is in a state of beingcontained only in concave portion 22 d of pressure-receiving part 22 aand in circular concave portion 23 b of cylinder end wall 23 and thusbecomes compressed at high pressure.

Normally, pressure-receiving means 22 is forced to the protrudingposition by the gas pressure in gas actuating chamber 21, and outputpiston 12 is also in its protruding position. In this state, thespecified pressure (for example, 7 Mpa) for the gas pressure in gasactuating chamber 21 is established. To bring the gas pressure of thegas actuating chamber 21 up to the above-mentioned specified pressure,compressed gas G is supplied to gas actuating chamber 21 fromabove-mentioned compressed gas supply source, via check valve 24.

In pressure-receiving means 22, because the pressure-receiving surfacearea which receives the pressure of compressed gas G (thecross-sectional area of pressure-receiving part 22 a) is larger (forexample, approx. 5 times) than the pressurized surface (cross section ofrod 22 b) pressurized by oil L, oil L in oil chamber 11 is pressured bythat factor to a higher pressure (for example, 35 MPa) thanabove-mentioned gas pressure (for example, 7 MPa).

With this fluid pressure cylinder 1, it is possible, by means of gasspring 3, to pressurize oil L in oil chamber 11 of oil pressure cylinder2 to a higher pressure than the gas pressure in the gas actuatingchamber 21 of gas spring 3, and as a result, to be able to generate astrong pushing force. Compressed gas is filled into gas actuatingchamber 21 from existing compressed gas delivery sources, such as gastanks, and, by means of the pushing force of gas spring 3, the hydraulicpressure of oil chamber 11 will be increased by a multiple of severaltimes and above-mentioned strong pushing force is generated. As aresult, the structure of fluid pressure cylinder 1, which has a springfunction, can be made smaller and benefits are gained in terms ofpreventing leakage of compressed gas G and achieving reduced productioncost.

Because cylinder part 20 of gas spring 3 is formed integrally withcylinder body 10 of hydraulic pressure cylinder 2 (by making a commoncylinder main body 4), and because gas spring 3 and hydraulic cylinder 2are arranged in a straight row, fluid pressure cylinder 1 can be made ina simple structure. As a result, production costs are reduced.

Inside cylinder body 10, a partitioning means 13 is provided which formsa partition between oil chamber 11 and gas actuating chamber 21. Becausethis partitioning means 13 is secured by thread fitting it into cylinderbody 10, it is simple to form oil chamber 11 and gas actuating chamber21 inside cylinder body 10 which is integrally formed with cylinder part20. In partitioning means 13, a passage hole 13 a is formed into whichoutput rod part 22 b of pressure-receiving means 22 is inserted suchthat it can slide freely. As a result, the end of output rod 22 acontacts oil L in oil chamber 11 and can surely pressurize oil L.

Next will be described various alternative embodiments of the presentinvention. Note that for items which are basically the same as inabove-mentioned embodiment, the same key number are used anddescriptions have been omitted.

First Alternate Embodiment

Referring to FIGS. 3 and 4, fluid pressure cylinder 1A of the firstalternative embodiment, has gas spring 3A provided with an oil chamberfor retraction 45 to cause pressure-receiving means 22 to retract,configured such that pressure-receiving means 22 is made to retract whenhydraulic pressure is provided to the oil chamber for retraction 45, andhydraulic cylinder 2A provided with a compressed coil spring 35 (springpart) which pushes output piston 32 toward the retraction side.

Cover wall 30 a of cylinder body 30 of hydraulic pressure cylinder 2A ismade thicker in the vertical direction than above-mentioned cover wall10 a. Within cover wall 30 a, a spring-seating hole 30 c is formed fromthe underside, with a diameter that is larger than passage hole 30 b.Compressed coil spring 35, mounted in spring-seating hole 30 c andfitting around rod 32 a of piston 32, elastically pushespressure-receiving part 32 b to the downward side (retracted position).

Furthermore, when compared to above-mentioned hydraulic pressurecylinder 2, rod 32 a of piston 32 is longer by the amount of theincreased thickness in cover wall 30 a in the vertical direction. Inthis way, the volume of oil chamber 31 is reduced, but it would also beacceptable to make the length of cylinder body 30 longer and the volumeof oil chamber 31 larger.

Oil chamber for retraction 45 is formed inside cylinder part 40 in thespace between partitioning means 13 and pressure-receiving part 22 a ofpressure-receiving means 22. Cylinder part 40 is formed with thickerwalls than above-mentioned cylinder part 20. Within cylinder part 40 isformed oil channel 46 a which connects to oil chamber for retraction 45and hydraulic pressure delivery port 46 b. Hydraulic pressure hose 48,extending from a hydraulic pressure supply unit 47, is connected to thishydraulic pressure delivery port 46 b, via connection plug 48 a.

With fluid pressure cylinder 1A, oil chamber for retraction 45 isprovided to retract pressure-receiving means 22. By providing hydraulicpressure to this oil chamber for retraction 45, pressure-receiving means22 is retracted. As a result, even without applying a very strongexternal force to output piston 32 in opposition to above-mentionedstrong pushing force, by providing comparatively low pressure hydraulicpressure to oil chamber for retraction 45, pressure-receiving means 22can be retracted easily. In addition, in hydraulic pressure cylinder 2A,compressed coil spring 35 is provided to apply a pushing force on piston32 in the return direction. As a result, by retractingpressure-receiving means 22, piston 32, in a linked motion, is surelymade to retract, through the pushing force of compressed coil spring 35.

Second Alternate Embodiment

Referring to FIG. 5, the second alternative embodiment, consists of aplurality of fluid pressure cylinders 1B positioned on a common baseplate 50. Each fluid pressure cylinder 1B has essentially the samestructure as above-mentioned fluid pressure cylinder 1A, but in thelower portion of cylinder part 55, flange 55 a is formed integrallytherewith. Flange 55 a is secured to the top surface of base plate 50 bymeans of a plurality of bolts 56, and check valve 24 is eliminated ingas passage hole 23 a of cylinder end wall 23.

A common gas passage 51 is formed in base plate 50 in the horizontaldirection. In the vertical direction, a plurality of branch gas passages52 connect to each of gas actuating chambers 21 of fluid pressurecylinders 1B via the gas passage hole 23 a thereof. Furthermore, inproximity to the connection of each gas passage hole of each fluidpressure cylinder 1B to branch gas passage 52, gas sealing is providedby one of O-ring 53, between cylinder end wall 23 and base plate 50.

At the gas supply end of common gas passage 51, a check valve 54 isbuilt in, common to the plurality of fluid pressure cylinders 1Bconnected to this common gas passage 51. Compressed gas fills the gasactuating chambers 21 of fluid pressure cylinders 1B, gas passage holes23 a, branch gas passages 52, and common gas passage 51. In other words,the gas pressure in the plurality of gas actuating chambers 21 of fluidpressure cylinders 1B is made uniform.

In addition, simply by providing the common check valve 54, a pluralityof gas actuating chambers 21 are filled with compressed gas in oneoperation, making it very easy to perform the work of charging thechambers with compressed gas. Furthermore, instead of a fluid pressurecylinder 1B, a fluid pressure cylinder essentially the same asabove-mentioned pressure cylinder 1A may be applied.

Third Alternate Embodiment

Referring to FIGS. 6 and 7, the third alternative embodiment appliesfluid cylinder 1C which is of the same construction as above-mentionedfluid pressure cylinder 1 as the output mechanism of a clampingapparatus 60. This clamping apparatus 60 comprises a base 61 and a clamparm 63, rotatably supported by a horizontal pivot shaft 62 on the topside of base 61. Base 61 has a vertical face 61 a, which can stop thework to be clamped W, and a support means 61 b of base 61, extendingfrom the lower side of vertical face 61 a, capable of supporting work tobe clamped W.

Clamp arm 63 consists of pushing arm 63 a, which extends from pivotshaft 62 beyond vertical face 61 a and can push work to be clamped Wagainst support means 61 b of base 61, and input arm 63 b, which extendsfrom pivot shaft 62 in the opposite direction as pushing arm 63 a. Fluidpressure cylinder 1C, fitted into the inside of mounting hole 61 cformed in base 61, inputs force to the end of input arm 63 b.

FIG. 6 shows clamping apparatus 60 in its clamped state, while FIG. 7shows clamping apparatus 60 in its clamp release state. In the clampedstate of FIG. 6, the strong pushing force of fluid pressure cylinder 1Cis conveyed from output rod 12 to clamp arm 63 and by means of thispushing force, clamp arm 63 is pushed to the clamped position and thework to be clamped W is strongly clamped.

From the state where clamp arm 63 is in its clamping position, if anexternal rod 65 for releasing the clamp is driven downward, output rod12 is pushed downward by this rod 65, via clamp arm 63, and retracts.Clamp arm 63 rotates to the clamp release position. In this state, quickunloading and reloading of work to be clamped W to the clamp setposition is performed. From this state, if rod 65 is driven upward,output rod 12 moves to protrude in an upward direction and clamp arm 63is driven from the clamp release position to the clamped position.

With this clamping apparatus 1, by applying fluid pressure cylinder 1 ofthis invention as the force output mechanism, it is possible to increasethe clamping force markedly, to clamp strongly the work to be clamped W.In addition, because fluid pressure cylinder 1, with its simplestructure, can be compactly built into base 61, and a big advantage isgained by making the overall clamping apparatus smaller.

Furthermore, instead of fluid pressure cylinder 1C, a fluid pressurecylinder essentially the same as above-mentioned fluid pressure cylinder1B could be applied. In this case, in fluid pressure cylinder 2A,compressed coil spring 35 is provided to force output piston 32 in theretract direction when hydraulic pressure is supplied to oil chamber forretraction 45 and pressure-receiving means 22 is retracted. As a result,external rod 65 for clamp release becomes unnecessary. However, it isdesirable to provide some form of a return mechanism, such as a spring,to cause clamp arm 63 to return to its clamp release position.

Forth Alternate Embodiment

Referring to FIGS. 8 through FIG. 10, the fourth alternativeimplementation applies the invention to a tool securing apparatus whichsecures tools at the end of the main shaft of a machine tool such thatthey can be released.

As shown in FIG. 8, the main shaft of a machine tool is supported by aplurality of bearings 71 a, so that it freely rotates. At the end of themain shaft is formed a tool holding bore 72 with a tapered shape suchthat the diameter is increasingly larger as its end is approached.

Tool securing apparatus 70 includes a collet 75, which engages matingportion of the base of tool T, such that it can be engaged ordisengaged. A draw bar 76 is linked to collet 75. A fluid pressurecylinder 1D, unique to this invention, pushes draw bar 76 to the “toolsecured” side (the base end side of main shaft 71). Release mechanism 90drives draw bar 76 to the “tool release” side (the distal end side ofmain shaft 71) in opposition to the pushing force of fluid pressurecylinder 1D.

In main shaft 71, tool holding bore 72, housing hole 80 in which collet75 is housed, passage hole 81 through which draw bar 76 passes, andcylinder attaching hole 82 are formed serially from the distal part tothe basal part of main shaft 71. Sleeve 83 is secured to the distal endof main shaft 71, by having its basal part fitted to the outside of mainshaft 71 by a threaded fit. Between the distal part of sleeve 83 andmain shaft 71, a plurality of holes 84 are formed. Mounted internally ineach hole, such that its base portion can slide freely, is a pushingmeans 85, the distal end thereof protruding in the direction of thedistal end of main shaft 71. By means of a plurality of plate springs86, inserted into holes 84, pushing means 85 are pushed toward theirdistal ends. Collet 75, having its distal end divided into 3 or 4sections, is configured as a divided body having elasticity. Collet 75has a shaft hole 75 a, through which draw bar 76 passes, and a largediameter hole 75 b with a diameter larger that shaft hole 75 a formed atthe distal end of shaft hole 75 a. Internally fitting in large diameterhole 75 b, is stopper 76 a, fixed at the distal end of draw bar 76.Here, tool T has an engaging part Ta and a large diameter disc Tc formedat the distal end of tapered shaft part Tb.

When draw bar 76 moves to the side where the tool is secured stopper 76a is stopped by the shoulder part 76 c at the border of shaft hole 75 a.Large diameter hole 75 b and collet 75 also move toward its basal end.Thereupon, the divided body of the distal end of collet 75 closes, whilemoving deeper into housing hole 80. On the way, collet 75 engages theengaging part Ta of tool T and, after engaging part Ta is pulled in thedirection of its basal end and in the state that tapered shaft part Tbof tool T comes to abut tool holding bore 72, the tool becomes secured.

When tapered shaft part Tb of tool T is secured in the disc part Tc oftool T is in state of being spring-loaded towards its distal end, due topushing means 85 with force applied by flat springs 86. When draw bar 76moves toward the release side, the stopped state of stopper 76 a againstshoulder part 75 c is released and tool T is pushed toward its distalend by pushing means 85 and is released. Also, the divided body of thedistal end of collet 75, which has elasticity, moves in the direction ofits distal end and as a result engaging part Ta of tool T is disengagedfrom collet 75 and tool T is released.

In other words, by applying pushing force on draw bar 76 in the toolsecuring direction (toward the basal end of main shaft 71) by means offluid pressure cylinder 1D, draw bar 76 is driven from the tool releaseposition to the tool secure position, draw bar 76 can be held in the“tool secure” position, and tool T can be secured in tool holding bore72.

Description of Fluid Pressure Cylinder 1D

Referring to FIGS. 9 and 10, fluid pressure cylinder 1D includes ahydraulic pressure cylinder 100 and a gas spring 101. Hydraulic pressurecylinder 100 and gas spring 101 have a common cylinder main body 103 andare arranged in a straight row pattern in the vertical direction.Cylinder main body 103 is fitted inside cylinder attaching hole 82 ofmain shaft 71 and is secured.

Hydraulic pressure cylinder 100 includes a cylinder body 110, whichmakes up about the upper half of cylinder main body 103, an oil chamber111, formed inside cylinder body 110 and filled with oil L, an outputpiston 112, which receives the hydraulic pressure of oil chamber 111,and a partitioning part 113, which forms the cylinder end wall. Apassage hole 110 b is formed in head cover 110 a of cylinder body 110. Ahollow rod part 112 a of output piston 112 is slidably inserted inpassage hole 110 b.

Output piston 112 has above-mentioned hollow rod part 112 a and apressure-receiving part 112 b made near the top end of hollow rod part112 a. Hollow rod part 112 a is externally fitted so that it slidesfreely on draw bar 76 and is also built so that it passes throughcylinder main body 103. Pressure-receiving part 112 b is fitted insidecylinder body 110 so that it can slide freely. Partitioning means 113extends toward the inside of cylinder body 110 and externally fits tothe outer surface of output part 122 b of pressure-receiving part 122 ofgas spring 101, so that output part 122 b can slide freely.

Gas spring 101 includes a cylinder 120, a gas actuating chamber 121,charged with compressed gas G and having an outer diameter slightlylarger than the diameter of above-mentioned oil chamber 111, apressure-receiving means 122 which receives the gas pressure of gasactuating chamber 121, and partitioning means 113 which, while forming ahead cover, is common to hydraulic pressure cylinder 100. Gas spring 101is configured to enable pressurizing oil L in oil chamber 111 ofhydraulic pressure cylinder 100 to a pressure higher thanabove-mentioned gas pressure. Cylinder 120 is formed integrally withcylinder body 110 of hydraulic pressure cylinder 100, makingabove-mentioned cylinder main body 103. By means of partitioning means113, oil chamber 111 is partitioned from gas actuating chamber 121.

Pressure-receiving means 122 is formed in a sleeve shape and isexternally fitted on hollow rod part 112 a at a location lower than thatof pressure-receiving part 122 b of output piston 112 and in a mannersuch that it can slide freely. Pressure-receiving means 122 haspressure-receiving part 122 a internally fitted in cylinder 120, so thatit slides freely, and output part 122 b, which extends upward from thispressure-receiving part 122 a. Output part 122 b passes through passagehole 113 a on the inside of partitioning means 113 and reaches oilchamber 111.

In cylinder end wall 120 a of cylinder 120, passage hole 120 b is formedand hollow rod part 112 a of output piston 112 is slidably internallyfitted to that passage hold 120 b. Near cylinder end wall 120 a, gaspassage hole 120 c is formed, communicating between gas actuationchamber 121 and the exterior. Into gas passage hole 120 c, check valve125 is internally fitted in a gas-tight manner. Furthermore, althoughnot shown in the figures, a venting hole is formed in cylinder 120,communicating to the gap between partitioning means 113 andpressure-receiving part 122 a. Seals 129 a˜129 h are also provided.

In fluid pressure cylinder 1D, oil L in oil chamber 111 of hydraulicpressure cylinder 100 can be pressurized, by means of gas spring 101, toa pressure higher than the gas pressure in gas actuating cylinder 121 ofgas spring 101. As a result, a strong pushing force, which could not begenerated by gas spring 101 alone, is generated by co-working withhydraulic pressure cylinder 100. This strong pushing force istransmitted from piston 112 to engaging shaft 76 b at the end of drawbar 76 which engages at the end of piston 112, enabling a strong pushingforce to be applied to draw bar 76 in the “tool securing” direction.This enables tool T to be secured with a strong force. In addition, itbasically performs the same functions and produces the same results asabove-mentioned embodiments.

Furthermore, releasing mechanism 90, as shown in FIG. 8, is provided ina fixed manner at the base side of main shaft 71. Releasing mechanism 90has a hydraulic pressure cylinder 91 which is controlled by a drivecontrol means which includes a supply source for hydraulic pressure. Thedrive control means is configured to push engaging shaft 76 b of drawbar 76 with the end of piston rod 91 a, thus pushing piston 112(pressure-receiving means 122) back into its retracted position at thebasal end and also, driving draw bar 76 in the “release” direction.

Fifth Alternate Embodiment

Referring to FIG. 11, the fluid pressure cylinder of the fifthembodiment is a fluid cylinder of the same basic structure asabove-mentioned fluid pressure cylinder 1 wherein a bellows 130, forexample of stainless steel, is mounted in gas actuation chamber 21.Bellows 130 is charged with compressed gas, and pressure-receiving means22 receives the pressure of this gas pressure via bellows 130. Gaspassage hole 23 a, in which a check valve is built in, communicates withthe interior of bellows 130 in a gas-tight manner. To achieve that, thebase surface of bellows 130 and the top surface of cylinder end wall 23may be bonded or a suitable sealing means may be mounted in proximity tothe connection point between bellows 130 and gas passage hole 23 a.

In this way, because bellows 130 is mounted to gas actuating chamber 21and bellows 130 is filled with compressed gas, there is almost no gasleakage of the compressed gas during long periods of use. This resultsin a stable pushing force being achieved during long periods. Becausebellows 130 can be charged with gas after bellows 130 is mounted insidegas actuating chamber 21, assembling bellows 130 is also easy.Furthermore, above-mentioned fluid pressure cylinders 1A˜1D could alsobe configured to have a bellow of a suitable structure mounted in theirgas actuating chambers and those bellows charged with compressed gas.However, the bellows mounted in gas actuating chamber 121 of fluidpressure cylinder ID is configured in a circular shape.

Finally, variations of above-mentioned embodiment and alternativeembodiments will be described.

Cylinder and cylinder main body may be formed as separate units. Also,the cylinder and cylinder main body may be connected by threading, etc.to form one body. Also, it is not absolutely necessary to arrange thegas spring an hydraulic pressure cylinder in a straight row pattern. Inthe fluid pressure cylinder of FIGS. 1˜7, the pressure-receiving part ofthe output piston may be internally fitted in the cylinder main body sothat it can slide freely. In this case, a venting hole is formed,communicating to the space between the pressure-receiving part and thecover wall. Also, a gas accommodating hole capable of accommodatingcompressed gas may be formed in the output rod of the pressure-receivingmeans.

In addition, embodiments with a variety of variations added to theabove-mentioned embodiment and alternative embodiments could beimplemented in a range that does not deviate from the substance of thisinvention. Also, besides use as a shock-absorbing mechanism, etc. forpress machines or as an outputting mechanism for clamping apparatuses,etc. this invention can be applied to various apparatuses and mechanismsthat require a pushing function.

According to the present invention, a gas spring is provided, comprisinga gas actuating chamber filled with compressed gas and apressure-receiving means which receives the gas pressure of a gasactuating chamber, and by means of this gas spring, the liquid in aliquid chamber of a liquid pressure cylinder can be pressurized to apressure higher than above-mentioned gas pressure. As a result, a strongpushing force can be generated and heavy loads supported. The gasactuating chamber is charged with compressed gas from an existingcompressed gas supply source, such as a gas tank, and by means of thepushing force of the gas spring, the liquid pressure of the liquidchamber is intensified by a factor of several times, enabling generationof above-mentioned strong pushing force. As a result, the structure ofliquid pressure cylinders having a spring function can be reduced insize and advantages are also obtained in regard to preventing leaks ofcompressed gas and in enabling reduced production cost.

According to a feature of the present invention, the cylinder part ofthe gas spring is formed integrally with above-mentioned cylinder bodyand gas spring and liquid pressure cylinder are arranged in a straightrow pattern. As a result pressure it is possible to make a fluidpressure cylinder with pressure-intensifying function having a simplestructure and to achieve reduced production cost.

According to another feature of the present invention, interior to thecylinder body a partitioning means is provided which separates theliquid chamber and gas actuating chamber. Because this partitioningmeans is secured in the cylinder body by a threaded fit, it is simple toform a liquid chamber and gas actuating chamber inside cylinder part andcylinder body which are formed integrally.

According to a further feature of the present invention, because apassage hole is formed in the separating means, through which the outputrod of the pressure-receiving means passes in a freely sliding manner,the end of the output rod can be made to contact the liquid in theliquid chamber and to surely pressurize the liquid.

According to another feature of the present invention, a liquid chamberfor retraction is made in order to retract the pressure-receiving means.Because the pressure-receiving means is retracted by supplying liquidpressure to this liquid chamber for retraction, it is possible toretract the pressure-receiving means easily by supplying liquid pressureof a relatively low pressure to the liquid chamber for retraction,without applying a very strong external force to the output piston. In alinked motion, it is possible to retract the output piston.

According to still a further feature of the present invention, because aspring which pushes the piston in the retract direction is provided, itis possible to reliably retract the output piston by means of thepushing force of the spring along with retraction of thepressure-receiving means.

According to another feature of the present invention, becauseabove-mentioned liquid chamber for retraction is formed between thepressure-receiving part of the pressure receiving means and thepartitioning means, it is possible to make the pressure-receiving partof the pressure receiving means receive the liquid pressure of theliquid chamber for retraction and, by supplying hydraulic pressure of acomparatively low pressure to the liquid chamber for retraction, toretract the pressure-receiving means.

Having described preferred embodiments of the invention with referenceto the accompanying drawings, it is to be understood that the inventionis not limited to those precise embodiments, and that various changesand modifications may be effected therein by one skilled in the artwithout departing from the scope or spirit of the invention as definedin the appended claims.

What is claimed is:
 1. A fluid pressure cylinder with pressureintensifying function comprising: a cylinder body; a liquid chamberwithin said cylinder body, said liquid chamber filled with liquid; anoutput piston which receives liquid pressure from said liquid chamber; agas spring having a gas actuating chamber, filled with compressed gas,and a pressure-receiving means, which receives gas pressure of said gasactuating chamber; said gas spring pressurizes said liquid in saidliquid chamber to a pressure higher than said gas pressure; a checkvalve inserted into said cylinder body and connecting said gas actuatingchamber to an exterior of said cylinder body; a partitioning meansinternal to said cylinder body, separating said liquid chamber and saidgas actuating chamber; said partitioning means being secured to thecylinder body by a threaded fit; a passage hole in said partitioningmeans; and an output rod part of the pressure-receiving means isinserted in said passage hole such that it slides freely.
 2. The fluidpressure cylinder with pressure intensifying function according to claim1, further comprising; a cylinder part of said gas spring is integralwith said cylinder body; and said gas spring and said liquid chamber arearranged in a substantially straight row.
 3. The fluid pressure cylinderwith pressure intensifying function according to claim 1, wherein saidpartitioning means is secured along a substantial portion of its axiallength to the cylinder body.
 4. A fluid pressure cylinder with pressureintensifying function, comprising: a cylinder body; a liquid chamberwithin said cylinder body, said liquid chamber filled with liquid; anoutput piston which receives liquid pressure from said liquid chamber; agas spring having a gas actuating chamber, filled with compressed gas,and a pressure-receiving means, which receives gas pressure of said gasactuating chamber, said gas spring pressurizes said liquid in saidliquid chamber to a pressure higher than said gas pressure; apartitioning means internal to said cylinder body, separating saidliquid chamber and said gas actuating chamber; a passage hole in saidpartitioning means; and an output rod part of the pressure-receivingmeans; said output rod part being inserted in said passage hole suchthat it slides freely.
 5. The fluid pressure cylinder with pressureintensifying function according to claim 4, further comprising: a liquidchamber for retraction in said gas spring for retracting saidpressure-receiving means; and said pressure-receiving means is retractedby supplying liquid pressure to said liquid chamber for retraction. 6.The fluid pressure cylinder with pressure intensifying functionaccording to claim 5, further comprising a spring for applying a pushingforce on said output piston in a retract direction.
 7. The fluidpressure cylinder with pressure intensifying function according to claim5, wherein said liquid chamber for retraction is formed between saidpartitioning means and said pressure-receiving part of saidpressure-receiving means.
 8. The fluid pressure cylinder with pressureintensifying function according to claim 6, wherein said liquid chamberfor retraction is formed between said partitioning means and saidpressure-receiving part of said pressure-receiving means.
 9. The fluidpressure cylinder with pressure intensifying function according to claim4, further comprising: a check valve communicating between an exteriorand interior of said gas actuating chamber.